The carcinogenicity of the polycyclic aromatic hydrocarbons is determined by a complex interaction of many genetic and environmental factors. The objective of this proposal is to gain some understanding of the mechanisms of hydrocarbon-induced carcinogenesis by measuring in a model system, hamster embryo cell cultures, specific biological changes produced by the hydrocarbons and the various aspects of cell-carcinogen interactions that lead to these changes. The levels of aryl hydrocarbon hydroxylase activity, the extent of hydrocarbon metabolism, the metabolite profiles, and the amounts and types of hydrocarbon DNA-bound products, under different experimental conditions, will be compared to the frequencies of hydrocarbon-induced transformation, mutation and cytoxicity. In this way, those aspects of cell-carcinogen interaction that are related to the induction of each of the biological effects in these cells will be defined.